Control circuit



Dec. 27, 1949 s. c. CORONITI 2,492,685

CONTROL CIRCUIT Original Filed July 28, 1943 2 Sheets-Sheet 1 9'! 4 @iai9/5 1, /5 5;

INVENTOR I Jamue/ 6160/00/77 dz'y RNE Y S. C. CQRONITI CONTROL CIRCUITDec. 27, 1949 2 Sheets-Sheet 2 Original Filed July 28, 1945 INVENTOR.Jame/C Cam/m? 1 ATZ ORNEY Patented Dec. 27, 1949 UNITED: STATES? OFFICECONT OL RCUIT. Samuel C:Coroniti,.Johnson City, N'.-Y., assignorcto-General-Aniline & Filmflotlm ation, New... York, N. Y., a corporationoi' Delavyare. Original application July 28; 1943, Serial No.

496,383. Dividedand-this application Jiiiief'lf 1944, Serial No. 539,045

4 Claims. (Cl. 250-27) invention-relatesto electronic control cirJuly-;28,-;l9$3,- and-issued December 24, 1946,- as.v

ten 0.- Al3i218: cr1--" otc raphi appae.

tes an le cnt el sc n uiaian as i ed. to, the assignee of, the present Iinvention.

While-the einyention .is of general applicabib. itsfind rar icular u eiahcto r phcapn ratus. A particular application of the. principles of theinvention is tov control the second exposure of arphctgographic film,such as :a movingpic-, Hence, for purposes oirillustratiom only,- theinvention will be described more par? .1 ticul-arlywith referencetouitscuse in a second;

ture i'llm.

exposure (30 201 apparatus.

Ina continuous process for treating motion pic.-.

ture film, the latent image,- produced-on a film.

exposedin a camera, is developed :into a. silver The; silver image isthen removed, and the film is cleared :of residual salts, thereby beingagain rendered -sen-:.

image; producing anegative print.

SitiVfitOligh'tr, The, image isthen examined, and.

the film is subjected'toa controlled printing light;

redeveloped and flXGdz to bring out;- a positive ima g.e.-.Ira-.thisprucess,v both the negative and they positive prints areformed: on the original film.

It is. amongthe objects .of this invention to provide an electroniccontrol circuit efiective. to con-,

trol the output of an electronic dischargetube in accordance with thevalueof a given condie. tion; to provide a control circuit for anelectronic 1 discharge tube in which the average current out-vput;of*the tube is variedbyvarying the phase. relation between the gridvoltage and the anode voltage; to provide means for controlling theoutputof, an electronic. discharge tube by impressingvoltages .ofsubstantially the same magnitudeon thegrid and anodeand varying therelative phase, relation ofsuch voltages to control the average;

current output ofthe tube; to provide a con.- trol circuit ;for varyingthe average current out.-.

put of=-an-- electronic discharge tube, in which electronicmeans areprovided forvarying the.

phase relation between the grid and anodevoltages. of said- -tube tocontrol the... current outp.ut.=. 7 provide such control circuit,includ-.. .ing-a tend-men: recess ve; e nt r ary n themternal resis nc-0f. le ron-1. me ns. n-

tube to varj the phase of the grid voltage with respect tothaanoderoltage, applied to the tube,..

to control thearerage. current output of the tube; to provideanelectronic control circuit for varying the average .current .output ofan electronic tube in accordancewiththe value of a given condition,- andincluding.,time..delay meansfor delaying the. response .of thecontrolsystem with. respect to variations .in such given. condition; and-v toprovide an.improved-electronic control circuit.

Theserand..otherobjects, advantages and features of :the .inventionwill.hex-apparent from the following description. and accompanying draw..-.

ings. In .the drawings:

Fig. 1 is .a vertical. sectional view through photographic.apparatus-with which the control cir-. cuit :oithe'. invention v isadapted to be used.

Fig. 2 is a diagrammatic representation of the apparatus-shown in-Fig;-1, and-the control circuit of the. invention...

Fig..-3.is a simplified electrical diagram of the fundamental-componentsof the. control circuit.

Fig. 4 =isuawsetaoficurves illustrating voltage.

and means are provided for. varying the relative. values of suchresistance and capacitance to vary.

the. .phase...of thegrid voltage with respect to thesphase of the.vanoderorxplate voltage. Such variation determines the. portion of eachcycle ofalternating-current-during which the tube is activated tosupplycurrentto. the load. Preferably,. theresistance inthegrid circuitcomprises an electronic tube whose internal resistance is varied bysuitable variation in the grid bias of the tube. The grid bias of thislast-named electronic tube is controlled inaccordance with the value oia given condition, and timedelay means are proviq ssii rd er ue. iii rponseb 51.150011? trol circuit to changsin the valueof the givencondition for, predetermined interval. While;

the. .electronic. ntrol circ tisoigeneral application. will.- scrib ed.s; -apn an medies a s nd. asdescribedin my sci a aaaiaaiaea.

be understood thatsuch embodiment of the prinpurposes oi .umamnen. bede- Hbwe e 9x11 1 ciples of the invention is exemplary only, and thatthe invention is not limited thereto.

Generally speaking, in applying the principles of the present inventionto such photographic apparatus, a film which has been exposed in acamera and then developed, fixed and bleached, is moved longitudinallypast an element effective to measure the optical density of the film.After passing this element, the film is moved past a variable intensitylight source. The optical density measuring element, through the elec-.tronic control circuit of the invention, controls the intensity of thevariable intensity light source. Means are provided in the controlcircuit for delaying the effect of the measuring element on the variableintensity. lightsource for a sufficient period of time to permit thefilmto travel from a point adjacent the measuring element to a pointadjacent the variable intensity light source.

Referring to Fig. 1 of the drawings, the illustrated photographicapparatus includes a light proof housing Ill'subdivided by partitions IIand I2 into compartments 13, I4' and I5. An intermediate wall Ili of thehousing It is formed with three apertures I1, I8 and I9, each disposedcentrally of one of the compartments l3, I4 and I5. I-Iousing'IO isformed with an extension 2I opposite the compartment I3 and with anouter wall 22 spaced from the wall I 6. Walls I6 and 22 form a tunnelthrough which passes the film 20 which is to be given a second exposure.

A relatively small constant voltage lamp 25 is mounted in housing I3.The light from lamp 25 is directed by a mirror 23 through aperture I1upon a photoelectric cell 3!! mounted in extension 2!. The particularphotoelectric cell=il1ustrated is responsive to far red and infra redrays, and has a substantially linear response to such rays. A red lightfilter 2.4 is mounted in brackets 26 adjacent aperture I1 and a Mattebase 21 is inserted in aperture I1. Through the control circuit shown inFig. 2, photoelectric cell 3!! controls the illumination'of a variablevoltage lamp 35 mounted in compartment I4; and which is adapted to givea variable intensity exposure to film 2!) through aperture I8. Ifdesired: a constant voltage lamp 4!) may be mounted in compartment I togive a constant intensity exposure to film 2! through aperture I9. Thecontrol of these lamps will be described more fully hereinafter. I Y

The film 20 travels in the direction of the arrow shown in Fig. l. Thefilm first passes over a roller 28 and then between walls Ifi'and 22. Atthe opposite end of the housing, film 2!] is threaded over a secondroller 3|. The film is maintained in constant spaced relation withrespect'to light 25 and photoelectric cell 36 by means of a guidebracket 32 which presses the film against spaced rollers 33', 34 as thefilm passes aperture I1.

The operation of the control circuit of the invention, as incorporatedin the described apparatus, will be apparent from a consideration ofFig. 2. In this figure, the elements shown in Fig. 1 have been given thesame reference characters. of the invention, film 213 Will have beenexposed in a camera, developed and fixed to form a negative image, andthen bleached before reaching the roll 28. I1 at which point lightrays-from lamp 25 pass through filter 24 and base 21 onto photoelectriccell 30. Through the control-circuit shown Before passing through theapparatus It then passes'in front'of aperture in Fig. 2, the operationof which will be described more fully, photoelectric cell 30 controlsthe intensity of ilumination of variable intensity lamp Thus, as film 20passes aperture 18, it receives an exposure from lamp 35 which is afunction of the optical density of the film as measured by photoelectriccell 39. 'Generally, the intensity of the second exposure given by lamp35 should be an inverse logarithmic function of the optical density ofthe film as measured by photoelectric cell at for reasons apparent to'those skilled in the art. The control circuit includes means fordelaying the response of lamp 35 to the measurements of photoelectriccell 30 for a period of time sufficient for a given point on the film tomove from aperture I1 to aperture I8.

After passing aperture I 8. film 23 may be given a constantpredetermined basic exposure at aperture I9 from constant intensity lamp40, if desired. The film then passes over roller 3|, after which it isagain developed, fixed and washed to form a positive image on the film.Subsequent to such treatment, the film may be examined in any well knownmanner and is then ready for use in a projector.

Referring to the control circuit shown in Fig, 2, lamps 25, 35 and 40are energized from a suitable reference source of alternating current 36which is connected to conductors 31 through a switch 38 and a fuse 4|.Lamp 25 is operated at a lesser voltage than lamps 35 and 40. It istherefore connected to the secondary winding 42 of a stepdowntransformer 43 connected to conductors 31. The energization of variableintensity lamp 35 is controlled by the photoelectric cell 30 throughelectronic control circuit of the invention. Constant intensity lamp 40is connected across conductors 31 and has a variable resistor 44 inseries therewith, so that the predetermined basic intensity of lamp 40may be selected to give a desired basic exposure to film 2D.

Alternating current energy for the control circuit is derived from atransformer 46 having a primary winding 41 connected by conductors 48 toconductors 31. A substantially constant direct current potential for thecontrol circuit is sup- 1 and 53. From the junction 54 of theseresistances,

a voltage is applied to anode 55 of photoelectric cell 30 through aresistor 5'5, and. a conductor 51.

Cathode 5B of photoelectric cell 30 is connected by conductor 8! tocontrol grid 62 of a thermionic amplifier or control tube 60. For apurpose to be described, a condenser 63 and a resistance (54 areconnected to conductor BI in parallel with each other. The opposite endsof condenser 53 and resistor I54 are connected by a conductor 65 toground. A suitable bias voltage for grid 52 of tube 60 is derived fromthe adjustable terminal 56 of resistor or potentiometer 61, connected bya conductor 68 to positive terminal 5! of direct current source 55,through conductor 13.

The anode-cathode circuit of amplifier tube 60 is connected to the gridcircuit of a grid controlled gaseous space discharge tube 15, such as athyratron tube. In a manner to be described, amplifier tube 60 iseffective in varying the phase relation of the 'vO1tages'app1ied-t0the.grid and plate, respectively, ,of I discharge tube vPi. A-conductr 13conneetscathodel I of tube fillntoia junction-point 14. sOne terminal J6of l the. secondarywinding T! of transformer disconnected to junctionpoint l4 lthroughia fixedcondenser 80. The igniting 01' grid-electrodeBI of tube '15 is connected to.junction point 14 nthroughsa grid currentlimitingresistor;:82.- The anode plate 33 of thermionic amplifier 3015connected to .the. opposite terminal 84 of secondary winding 11 througha load resistancer86.

Theacathode 81 of thyratron tube '15 .is -.connectedto the midvpoint 88of.secondar,y winding TI. l'Plate 9]! of tube 1151s connected .by a.conductor l9! to one terminal of lamp 35. The opposite terminal of lamp35 is-connected through conductor 92, fixed resistance 33 and .tuse 94to terminal. ofsecondary winding 1], For a purpose to berdescribed, thescreen. gridelectrode 95, of amplifierltube fi'll is connected through alimiting resistor T96 to,platei3'3', and afixedresistoril'l isconnectedacross the output ofamplifler B0.

Erom the .above description of the circuit, it will lbe observed,thatithe control tube 69 derives its .operating anode potential fromvthe charging currentof the condenser .30 (at operating .half cycles-Whenthe terminal 34 .is positive with respent-Ito the terminal .16 ofthe winding 11. In efiect, Lthe load resistance 86 land the. fixedresistor 91,1together Withlthe condenser 80 form a voltage divideracrossi-the alternating currentsource represented here by the secondarywinding k'lliof the transformer 45. Atinoperative .halfcycles when theterminal I84 is negative withrespect to the terminal 16 of the windingH, the discharge or reverse current of the condenser finds a .paththrough-theresistors 9'! land 36. The control tube 60 is,-.of course,non-conductive at suchperiods.

The operation of the circuit illustrated inFig. 2 is effective :to varythe illumination of lamp 35 in accordance with the value of agivencondition, such as the amount of light falling on photoelectric cell 30from lamp .25 as film passes aperture l1. It will be noted that thevoltage applied to igniting grid electrode 8| of discharge tube'15'isderived from junction point 14. Junctionpoint Mis the connecting pointbetween amplifier tube .60 and condenserBl), which .are thus connectedin series with'the secondary winding 11 of transformer 46. Theinternalresistance of amplifier'tube 60 is dependent upon'the voltage applied toits grid electrode 62. Thus, with condenser 88 being relatively fixed,variations in the. voltage applied to grid 62 will varytheinternalresistance of "amplifier tube 60. This, in turn, will varythe phase ofthe voltage applied to grid 8| with respect to the voltage applied toplate 90 of thyratron 15. The plate voltage is derived from the samealternating current reference source as. is the grid vvoltage;

The; voltage across secondary winding" is the vector sum of the voltagesacross amplifier tube 60 and condenser 89. The alternating-voltagebetween the grid and the cathode of thyratron I5 is constant inmagnitude as'will be made apparent hereinafter. However, the phaserelation of'the gridto cathode'voltage'with respect to the outputvoltage of tube l5'is controlled 'byth'e condenser 80 and amplifier tube60. By varying the effective conductivity of amplifiertfi, the phaserelation of the igniting of grid electrode voltage of discharge tubewith respect to the plate voltage thereof is changed. The thyratron 1.5is thus made .to fire at a point duringeach cycle of applied ,platevoltcontrol circuit is delayed for this interval. is accomplishedby atime delay circuit including I condenser 6-3 andi-resistance M which arecon nectedin .parallel with the'control grid-62 of amage when :theinstantaneous value :ofthe igniting electrode voltage exceeds thecritical firing value. The .-firingof tube 1 1.5 is thus =made dependenton the :phase relation between I its applied-grid-cathode, :or inputvoltage, and its applied :plate to cathode, or output :voltage.

The internal resistance -and thereby the 'efi'ective conductivity oftube 60 is a function 'of the amount of light reaching zphotoelectriccell 30.

As theamount of light falling on-cell30 increases, for instance,thecurrent flow through anode .re-

sistor =56 increases. This increases the voltage drop across resistor-SBand thus varies the volt-- age-applied to grid electrodeBZof amplifiertube.

60. The internal resistance of tube 60 is :thus

madedependent-on the amount-of light reaching i,

-As mentioned above, the output of tube 6D, for correspondingly itsefiective resistance zas-applied to the input circuit-of tube 15, variesthe relative phase relationbetween thephotoelectric cell 30.

input and output voltages of thyratron tube 15. This in turn determinesduring what portion of each operating whalf cycle of applied platevoltage tube l5 will be conductive. As-lamp 35 is inseries withtheoutput-0f :tube 15, itseaverage intensityof illumination is accordinglycontrolled-as (a function of the elTectiVe resistance of amplifier tube68. This action is described in detail hereinafter withreference toFigs.3, land 5. 1

Bysel-ection of an amplifier .tube60 with :suit- I of amplifier 60maybeaccomplished in any de-;

sired manner. In one practical embodiment of the 'invention, a pentode101" the type -6F'6 has been used satisfactorily as amplifier tube 60.]

The design of the parameters of the circuits' of tube 60 is-improved bythe use of'the screengrid resistor96- and shunt resistorSTconnected-across the outputcf tubeiill. In the describedrembodlment,'-with the use of 'a red light filter .14, a red light.responsive photoelectric cell 30 having .a 5 linear response, and apentode for amplifier 60,

the circuit aparameters necessary to produce proper control of :lamp 35are effectively obtained in practice.-

One other criterion is taken into consideration 3 in the operation ofthe illustrated apparatus. It I takes'a 'smalliinterval of time for :-agivenpoint on film =29 to move from adjacent aperture I 1 to adjacentaperture la The imposition of the control signal from e-photoelectriccell 30 on the This plifier tube 60 and photoelectric cell 30. By properselection of the relative sizes of condenser 63 and resistanceMgtheproper timedelay in the impression 'of the control signal fromphotoelectric 'cell 30' on the control grid 62 of tube '68 is obtained.

Figs. 3, :4 and -5 diagrammatically illustrate the general principlesunderlying thaelectronic.

control circuit of the present invention. The

potential, such :as the terminals of winding 11 of transformer 46,junction point 14 and mid-point 88 of winding 11 have been alsodesignated with the letters a, b, c, and d, respectively. Variableintensity lamp 35 is represented by resistance Rp and the output effectof amplifier 60 by variable resistance Rg. Also, the potentialdifierences between the respective points have been designated Eda, Ebd,Ede and Elie.

In Fig. 4 are curves illustrating the operation of the circuit throughtwo cycles. The grid voltage Ede, is represented by the broken linecurve G. The output voltage of tube 15 is represented by the solid linecurve P. In the instant illustration, the grid voltage G lags the plateor output voltage P by electrical degrees. The grid voltage G mustobtain a certain critical value K before tube 15 can become conductiveor fire. As shown in Fig. 4, the plate voltage obtained the positivepotential Z) at the time the grid attains its critical potential K andtube 15 starts to fire. Tube 15 continues to fire for the rest of thepositive half cycle, to point M. Tube 15 remains nonconducting until itsplate voltage P reaches the value Z' f', when the grid voltage G againreaches the magnitude k. The tube 15 will again become conductive andremain conductive for the remaining half cycle to point M.

The conducting time Zm of tube 15 may be made smaller or larger byvarying the electrical phase displacement of the grid voltage G withrespect to the plate voltage P. In Fig. 4, this would be represented byshifting curve G to the right or the left with respect to curve P. Themaximum time for conduction of tube 15 is practically for a completehalf cycle or about 180. Thus, by varying the phase difference betweenthe plate and grid voltages of tube 15, the amount of time during whichtube 15 is conductive is correspondingly varied.

Fig. 5 is a vector diagram of the relation of phase angle and the gridand plate voltages Ede and Eda. The current I flowing through theresistance H and condenser 80 here leads the voltage Eba acrosstransformer winding 11 by an angle a. The voltage drop Ede acrossresistance Rg is in phase with current I. The voltage Ecb acrosscondenser 80 lags 90 with respect to cur-- rent I. The vector sum of thevoltages E56 and Ecb is equal to the total voltage Eds. of the secondaryll of transformer 46. This relation holds for all conditions. Thevectors Ecb and Eac make a right angle with each other for all values ofthe angle Hence the locus of point 0 for all values of on from zero to90 will be a semi-circle with fixed vector Em as diameter.

The voltage between grid 8! and the cathode 81 of tube 15 is representedby the vector Edc which is a radius of such circle. Since the voltagesEbd and Eda are one-half of Eba, the magnitude of vector Ede is equal tothat of Ebd and Eda. Vector Edc is thus constant in magnitude for allsuch values of oz. either'a clockwise or a counter clockwise directionwill vary the relative magnitudes of the vectors Ebc and Ear, andlikewise, the phase angle between the plate voltage Eda and grid voltageEde. It will be apparent that either the voltage across the condenser 80or that across the resistance R; can be varied from zero to therespective full values of the transformer secondary voltage Elia; andthe phase angle thus varied from 0 to 180.

Referring again to Fig. 3, either resistance R3 may be held constant andcondenser 80 varied, or vice versa, to vary the phas relation of thegrid or input voltage of tube with respect to the Movement of vector Edein plate or output voltage thereof. As pointed out in connection withFig. 4, this correspondingly varies the time interval during which tubeI5 is conductive. In practice, either resistance Rg or condenser 80, orboth. may be varied manually, mechanically, electronically orautomatically. In the illustrated embodiment condenser 80 is heldconstant, and resistance Rg is electronically varied by amplifier tube60. In turn, tube 60 is herein automatically controlled by photoelectriccell 30.

Variations in the conductivity or internal resistance of amplifier tube60 as controlled by amount of light reaching photoelectric cell 30 willvary the phas relationship of the voltage applied to grid 8| of tube I5with respect to the voltage applied to plate thereof.

While a particular application of the control circuit including the timedelay circuit comprising condenser 63 and resistance 64, amplifier tube60, discharge tube 15, condenser 80, and the load comprising lamp 35 hasbeen described to illustrate the principles of the invention, thecircuit is of general application. That is, it may be used otherwisethan in the specific case illustrated in the drawings. It shouldtherefore be understood that while a specific embodiment of theinvention has been shown and described, to illustrate how the principlesof the invention may be applied, the invention is not limited thereto,but may be otherwise embodied without departing from the principlesthereof.

What I claim is:

1. In a control circuit for gaseous discharge devices having anode,cathode and an igniting electrode, a source of alternating current,circuit means for connecting a portion of said source between saidcathode and said anode including in series a load element, a phase shiftnetwork comprising a circuit connecting a por-v tion of said sourcebetween said igniting electrode and said cathod including a reactiveelement, and connecting said first mentioned portion of said sourcebetween cathode and said igniting electrode including a resistance, acontrol tube associated with said network having anode, cathode andcontrol electrodes, circuit means for deriving operating anode potentialfor said tube from said network including said resistance and meansassociated with the grid electrode of said tube for changing itsconductivity and thereby th relative phase-shift of said network.

2. In a control circuit for gaseous discharge devices having anode,cathode and an igniting electrode, a source of alternating current,circuit means for connecting a portion of said source between saidcathode and said anode including in series a load element, circuit meansfor connecting another portion of said source between said ignitingelectrode and said cathode including a reactive element, circuit meansfor connecting said first mentioned portion of said source betweencathode and said igniting electrode including in series a resistance andthe anode and cathode elements of a thermionic control tube whereby saidreactive element and said control tube in series are substantiallybetween terminals of said source and means for controlling the effectiveconductivity of said. tube and thereby the relative phase of the voltageapplied from said source to said igniting electrode with respect to thatapplied to another electrode of said device and a current conductiveconnection between the cathode and the anode of said tube.

amaces 3. In a control circuit for gaseous discharge devices havinganode, cathode and an igniting electrode, a source of alternatingcurrent, circuit means for connecting a portion of said source betweensaid cathode and said anode including in series a load element, circuitmeans for connecting another portion of said source between saidigniting electrode and said cathode including a reactive element,circuit means for connecting said first mentioned portion of said sourcebetween cathode and said igniting electrode including in series aresistance and the anode and cathode elements of a thermionic controltube whereby said reactive element and said control tube in series aresubstantially between terminals of said source and means for controllingthe effective conductivity of said device and thereby the relative phaseof the voltage applied from said source to said igniting electrode withrespect to that applied to the anode of said device and a resistancebridging the anode and cathode electrodes of said tube.

4. In a control circuit for gaseous discharge devices having an anode, acathode and an igniting electrode, a divided source of alternatingcurrent comprising a center tapped secondary winding of a transformer, aconnection from the cathode of said device to said center tap, aconnection from the anode of said device through a load resistance toone terminal of said winding, a voltage divider between terminals ofsaid winding comprising a resistance element and a condenser in seriesso proportioned as to form at the junction point of their connection avoltage terminal with respect to said tap which is displaced in phasewith respect to the terminals of said winding, a connection from saidigniting electrode to said junction point, a control tube having anode,

10 cathode and grid electrodes, a connection from the cathode of saidtube to said junction point and a connection from the anode of said tubeto a portion of said resistance element, whereby the portion of saidresistance element between anode of said tube and one terminal of saidwinding serves as a load resistance for said tube and the other portionof said resistance between anode and cathode of said tube provides areverse current path for said condenser, and a control circuit includingsaid grid electrode for changing the efiective conductivity of said tubeand thereby the relative phase displacement at said junction point.

SAMUEL C. CORONITI.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,005,892 Gulliksen June 25, 19352,010,577 Wilson Aug. 6, 1935 2,112,736 Cockrell Mar. 29, 1938 2,156,886Vedder May 2, 1939 2,269,324 Turner et a1. Jan. 6, 1942 2,274,158Penther Feb. 24, 1942 2,431,158 Yates Nov. 18, 1947 FOREIGN PATENTSNumber Country Date 747,996 France Apr. 10, 1933 OTHER REFERENCESElectron Tubes in Industry by Henny, 1st edition, page 362, Figure 89.(Copy in Division 54.)

